KR20220116501A - Process for the preparation of cyclohexanol and cyclohexanone - Google Patents

Abstract

The present invention relates to a process for preparing a mixture containing cyclohexanol and cyclohexanone, comprising the step of hydrogenating cyclohexyl hydroperoxide in cyclohexane in the presence of a Raney nickel catalyst to provide cyclohexanol and cyclohexanone it's about

Description

Process for the preparation of cyclohexanol and cyclohexanone

Several different processes are used to oxidize cyclohexane to a product mixture containing cyclohexanone and cyclohexanol. Such product mixtures are commonly referred to as KA oil (ketone/alcohol oil) mixtures. A very large proportion of KA oil is consumed for the production of nylon 6,6 and the precursor of nylon 6. KA oil mixtures can be easily oxidized to produce adipic acid, an important reactant in the manufacturing process of certain condensation polymers, especially polyamides, especially nylon 6,6. Given the large amounts of adipic acid consumed in these and other processes, there is a need for a cost-effective process for producing adipic acid and its precursors. In addition, cyclohexanol from KA oil can be dehydrogenated to give cyclohexanone, and cyclohexanone from dehydrogenation of KA oil and cyclohexanol can be preferably combined with hydroxylamine via cyclohexanoneoxime. can be reacted to provide epsilon-caprolactam.

The classic process for producing a mixture containing cyclohexanone and cyclohexanol is carried out in two steps to obtain KA oil via oxidation of cyclohexane. First, thermal auto-oxidation of cyclohexane leads to the formation of isolated cyclohexyl hydroperoxide (CyOOH). In the second step, KA oil is obtained through the decomposition of CyOOH catalyzed using chromium ions or cobalt ions as homogeneous catalysts.

With worldwide regulatory restrictions, the need for replacement of environmentally unfriendly catalysts such as chromium and cobalt catalysts is becoming more urgent. If current homogeneous catalysts can be replaced with non-toxic heterogeneous catalysts, the environmental footprint and economics of these processes can be significantly improved.

Various types of homogeneous catalysts are used to catalyze the oxidation of cyclohexane by hydroperoxide to produce KA oil. The heterogeneous catalytic process has the advantage of easy separation and has been reported to catalyze the oxidation of cyclohexane by hydroperoxide. Many heterogeneous catalysts are based on zeolite-like supports incorporating or embodying transition metals or noble metals, or oxide supports on which transition metals are deposited.

GB 964,869 discloses a process for the oxidation of liquid cyclohexane to cyclohexanol and cyclohexanone by free oxygen, in which the reaction mixture is reduced to convert cyclohexanone and cyclohexyl hydroperoxide to cyclohexanol is converted The reduction can be carried out by means of catalytic hydrogenation or chemical (non-catalytic) reducing agents. As hydrogenation catalysts, mention is made of catalysts based on nickel, copper, platinum, palladium, ruthenium and rhodium. The catalyst is preferably deposited on a solid support arranged in a fixed bed, and the material to be hydrogenated flows countercurrent to the hydrogen. As a chemical reducing agent, metals that liberate nascent hydrogen or hydrides such as alkali borohydride or lithium aluminum hydride on contact with the acid formed can be used.

US 3,479,394 discloses a method for preparing cyclohexanol and cyclohexanone by converting the hydroperoxide to cyclohexanol and cyclohexanone after stopping the oxidation when air oxidation of cyclohexane and a relatively low proportion of hydroperoxide are formed. process is initiated. This conversion is effected by chemical reduction by hydrogen in the presence of a catalyst, such as platinum or Raney nickel, or by a metal salt in which the metal is in its lowest valence state, such as ferrous sulphate. can receive

Gerd Dahlhoff et al.: "ε-Caprolactam: new by-product free synthesis routes", Catalysis Reviews: Science and Engineering, vol. 43, no. 4, pages 381-441 disclose that ε-caprolactam can be produced from cyclohexanone via cyclohexanoneoxime.

US 3,772,375 A discloses the hydrogenation of 6-hydroxyperoxyhexanoic acid separated from an aqueous wash of the product of oxidation of cyclohexane with molecular oxygen in the liquid phase. 6-hydroxyperoxyhexanoic acid is subjected to hydrogenation as such or as a salt contained in the aqueous phase in the presence of a catalyst consisting essentially of metallic palladium, rhodium or platinum.

US 3,937,735 describes the oxidation of cyclohexane with oxygen or oxygen-containing gas in the liquid phase to produce an oxidation reaction product containing cyclohexyl hydroperoxide, hydrogen gas-containing in the presence of a catalyst containing palladium, platinum, nickel or rhodium. catalytically hydrogenating the oxidation product in a hydrogenation zone using the stream to substantially convert cyclohexyl hydroperoxide to cyclohexanol, recovering a cyclohexanol fraction by distillation and converting the cyclohexanol to cyclohexanone and hydrogen A process for preparing cyclohexanone comprising the steps of: catalytic dehydrogenation with is starting. The catalyst is preferably deposited on a carrier such as aluminum oxide, carbon or silica. In the examples, a palladium catalyst supported in a fixed bed containing 0.1% by weight of palladium on aluminum oxide is used.

There remains a need for a process for the oxidation of cyclohexane to a product mixture containing cyclohexanone and cyclohexanol, which has high conversion of cyclohexane and high selectivity to KA oil at low catalyst production costs. It is an object of the present invention to provide such a process.

Summary of the invention

A mixture containing cyclohexanol and cyclohexanone comprising the step of hydrogenating cyclohexyl hydroperoxide in cyclohexane in the presence of a Raney nickel catalyst to provide cyclohexanol and cyclohexanone is solved by the manufacturing method of

Preferably, the method

a) oxidizing cyclohexane with molecular oxygen to provide a reaction mixture comprising cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, 6-hydroxyperoxycaproic acid and unconverted cyclohexane;

b) hydrogenating cyclohexyl hydroperoxide in the presence of a Raney nickel catalyst to provide cyclohexanol and cyclohexanone.

In one embodiment of the invention, step b) is carried out in the reaction mixture obtained in step a).

In another embodiment of the invention, prior to step b), the reaction mixture obtained in step a) is extracted with water to form an organic phase containing cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone and unconverted cyclohexane and An aqueous phase containing 6-hydroxyperoxycaproic acid is provided and step b) is carried out in an organic phase.

In a further embodiment of the invention, 6-hydroxyperoxycaproic acid is hydrogenated in the presence of a Raney nickel catalyst to provide 6-hydroxycaproic acid.

In a preferred embodiment, 6-hydroxyperoxycaproic acid is hydrogenated in the aqueous phase in the presence of a Raney nickel catalyst to provide 6-hydroxycaproic acid.

The present invention also relates to a process for the preparation of adipic acid,

a) oxidizing cyclohexane with molecular oxygen to provide a reaction mixture comprising cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, 6-hydroxyperoxycaproic acid and unconverted cyclohexane;

b) hydrogenating cyclohexyl hydroperoxide in the presence of a Raney nickel catalyst to provide cyclohexanol and cyclohexanone, and

c) optionally after purification by distillation, oxidation of cyclohexanol and cyclohexanone with nitric acid to give adipic acid.

The invention further relates to a process for the preparation of 6-hydroxycaproic acid, comprising the step of hydrogenating 6-hydroxyperoxycaproic acid in the presence of a Raney nickel catalyst.

Preferably, the method

a) oxidizing cyclohexane with molecular oxygen to provide a reaction mixture comprising cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, 6-hydroxyperoxycaproic acid and unconverted cyclohexane; and

b1) hydrogenating 6-hydroxyperoxycaproic acid in the presence of a Raney nickel catalyst to provide 6-hydroxycaproic acid.

In one embodiment, step b1) is carried out in the reaction mixture obtained in step a).

In a further embodiment, prior to step b1), the reaction mixture obtained in step a) is extracted with water to provide an organic phase containing cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone and unconverted cyclohexane and 6-hydro An aqueous phase containing hydroxyperoxycaproic acid is provided, and step b1) is carried out in the aqueous phase.

details

In general, in a first step a), cyclohexane is oxidized with molecular oxygen to cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, 6-hydroxyperoxycaproic acid, unconverted cyclohexane and possibly additional A reaction mixture comprising by-products is provided.

Step a) can be carried out by thermal auto-oxidation of cyclohexane with molecular oxygen, preferably in admixture with an inert gas, under pressure, such as 15-25 bar, and at elevated temperatures, such as 160-190° C.

In step b), cyclohexyl hydroperoxide is hydrogenated in the presence of a Raney nickel catalyst to give cyclohexanol and cyclohexanone.

In step b1) 6-hydroxyperoxycaproic acid can be hydrogenated in the presence of a Raney nickel catalyst to provide 6-hydroxycaproic acid. 6-hydroxyperoxycaproic acid can be hydrogenated simultaneously with cyclohexyl hydroperoxide in the same reaction mixture, or can be hydrogenated in a separate step b1) by separating hydroxyperoxycaproic acid from cyclohexyl hydroperoxide prior to hydrogenation. have.

Suitable Raney catalysts may have, for example, a BET surface of 80 to 120 m ² /g and may contain promoter elements such as zinc or chromium.

The Raney catalyst used in the present invention can be prepared in a conventional manner. Ni-Al alloys are made by dissolving nickel in molten aluminum and then cooling (“quenching”). A small amount of a third metal such as zinc or chromium may be added as a promoter to enhance the activity of the resulting catalyst. Accelerators can change the mixture from binary to ternary alloys, resulting in different quenching and leaching properties during activation.

In the activation process, the alloy, usually as a fine powder, is treated with a concentrated sodium hydroxide solution. The formation of sodium aluminate (Na[Al(OH) ₄ ]) requires a high concentration of sodium hydroxide solution. Sodium hydroxide solutions with a concentration of up to 5 M are commonly used. Typically, leaching proceeds between 70 and 110 °C.

In the practice of the invention, the catalyst may be slurried with the reaction mixture using techniques known in the art. The process of the invention is suitable for batch, semi-continuous or continuous cyclohexyl hydroperoxide hydrogenation. These processes can be carried out under a wide variety of conditions, as will be apparent to those skilled in the art.

Suitable reaction temperatures for the process of the invention typically range from about 20 to about 80°C or higher, advantageously from about 25 to about 60°C.

According to the invention the process is advantageously carried out at a hydrogen pressure of 0.1 MPa (1 bar) to 10 MPa (100 bar), preferably 0.1 MPa (1 bar) to 5 MPa (50 bar), such as 2 MPa (20 bar). is executed

At the end of the hydrogenation reaction, the target compound may be finally purified by a method well known in the art, such as distillation.

In a further step c), cyclohexanol and cyclohexanone can be oxidized with nitric acid to give adipic acid.

Step c) can be carried out by nitric acid oxidation of KA oil in concentrated nitric acid under atmospheric or elevated pressure. The reaction temperature is between 70 and 100°C. A homogeneous transition metal can catalyze the reaction. Adipic acid and by-products can be purified by series crystallization.

In a further step, the cyclohexanol can be dehydrogenated to provide additional cyclohexanone and the cyclohexanone can be converted to epsilon-caprolactam.

Accordingly, the invention also relates to a process for the preparation of epsilon-caprolactam,

a) oxidizing cyclohexane with molecular oxygen to provide a reaction mixture comprising cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, 6-hydroxyperoxycaproic acid and unconverted cyclohexane;

b) hydrogenating cyclohexyl hydroperoxide in the presence of a Raney nickel catalyst to provide cyclohexanol and cyclohexanone;

c) purifying cyclohexanol and cyclohexane optionally by distillation;

d) optionally separating cyclohexanone from cyclohexanol;

e) dehydrogenating cyclohexanol to cyclohexanone;

f) converting cyclohexanone to epsilon-caprolactam.

Preferably, in a further step, cyclohexanol can be dehydrogenated to provide additional cyclohexanone, which can be reacted with hydroxylamine to provide epsilon-caprolactam via cyclohexanoneoxime. . Accordingly, the present invention also relates to a process for the preparation of epsilon-caprolactam,

a) oxidizing cyclohexane with molecular oxygen to provide a reaction mixture comprising cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, 6-hydroxyperoxycaproic acid and unconverted cyclohexane;

b) hydrogenating cyclohexyl hydroperoxide in the presence of a Raney nickel catalyst to provide cyclohexanol and cyclohexanone;

c) purifying cyclohexanol and cyclohexanone optionally by distillation;

d) optionally separating cyclohexanone from cyclohexanol;

e) dehydrogenating cyclohexanol to cyclohexanone;

f1) reacting cyclohexanone with hydroxylamine or a salt thereof to give cyclohexanone oxime;

2) reacting cyclohexanone oxime to provide epsilon-caprolactam.

Step d) is optional. Refined KA oil containing cyclohexanol and cyclohexanone can be subjected to dehydrogenation without separation of cyclohexanone and cyclohexanol.

Step e) may proceed in the presence of a zinc or copper containing dehydrogenation catalyst, for example at 200 to 450° C., preferably at about 270° C.

Step f) is usually carried out with aqueous hydroxylamine sulfate or a buffer solution containing hydroxylamine and phosphoric acid.

Step g) (Beckmann-rearrangement) is usually carried out in the presence of concentrated sulfuric acid or fuming sulfuric acid, preferably at a temperature of 90 to 120° C. The lactam sulfate solution formed is neutralized primarily with ammonia to give the free lactam.

Additional methods for converting cyclohexanone to epsilon-caprolactam can be found in the literature.

The invention is further illustrated by the following examples. It is to be understood that the following examples are provided for illustrative purposes only, and are not used to limit the invention thereto.

Example

analysis

Yield and selectivity were determined using gas chromatography with internal standards. CyOOH in cyclohexane was quantified by iodine measurement.

Conversion = conversion of CyOOH, in the case of decomposition of CyOOH, conversion is defined as the number of moles of CyOOH consumed divided by the initial number of moles of CyOOH:

Conversion = 100 x nCyOOH (consumption)/nCyOOH (initial)

For the decomposition of CyOOH, selectivity is defined as the number of moles of cyclohexanol (CyOH) and cyclohexanone (CyO) produced divided by the number of moles of CyOOH consumed:

100 x (nCyOH(generation) + nCyO(generation))/nCyOOH(consumption)

Yield = conversion x selectivity

Raw material

Industrial reaction mixtures used in the examples:

1. Reaction mixture A , a mixture of cyclohexylhydroperoxide (CyOOH) and 6-hydroxyperoxycaproic acid (HPOCap): cyclohexane is oxidized to molecular oxygen or a mixture of molecular oxygen and other inert gases, CyOOH, A reaction mixture comprising cyclohexanol (CyOH), cyclohexanone (CyO), unconverted cyclohexane, HPOCap and other carboxylic acids and dicarboxylic acids having 1 to 6 carbon atoms as main components is provided.

Reaction mixture A, after addition of water to the washing column, is separated into an organic phase (reaction mixture B) and an aqueous phase (reaction mixture C).

2. Reaction mixture B , CyOOH: after washing reaction mixture A with water, the organic phase mainly consists of cyclohexane, cyclohexanone, cyclohexanol, CyOOH and other carboxylic acids and dicarboxylic acids having 1 to 6 carbon atoms .

3.

4. Reaction mixture C , HPOCap: After washing reaction mixture A with water, the aqueous phase consists mainly of HPOCap and other carboxylic acids and dicarboxylic acids having 1 to 6 carbon atoms.

Example 1 Conversion of Reaction Mixture B Using Current Industrial Chromium Based Catalysts

Reference experiments were run batchwise using a current industrial chromium based catalyst used to convert reaction mixture B to KA oil. 42.7 g of reaction mixture B containing approximately 6% cyclohexylhydroperoxide in cyclohexane was poured into a glass reactor equipped with Dean Stark filled with cyclohexane. The temperature was raised to 80° C. and 0.1 g of a solution containing 0.5% chromium catalyst was added to reaction mixture B. The results obtained are reported in the table below.

Conversion = conversion of CyOOH, in the case of decomposition of CyOOH, conversion is defined as the number of moles of CyOOH consumed divided by the initial number of moles of CyOOH:

Conversion = 100 x nCyOOH (consumption)/nCyOOH (initial)

For the decomposition of CyOOH, selectivity is defined as the number of moles of cyclohexanol (CyOH) and cyclohexanone (CyO) produced divided by the number of moles of CyOOH consumed:

100 x (nCyOH(generation) + nCyO(generation))/nCyOOH(consumption)

Yield = conversion x selectivity

The mole percentages of major by-products in the crude reaction mixture are reported as follows.

Example 2: General Procedure for Batch Hydrogenation of Reaction Mixture B over Nickel Raney Catalyst

In a dry atmosphere of N ₂ , 0.3 g of Nickel Raney catalyst was stirred in a hydrogenation autoclave with 68 g of reaction mixture B containing approximately 6% cyclohexylhydroperoxide in cyclohexane. The temperature was raised to 60° C. and the total hydrogen pressure was 20 bar. After 2 hours, the resulting crude reaction mixture was analyzed by gas chromatography. The results obtained are reported in the table below.

Since the starting reaction mixture B already contains impurities, hydrogenation of reaction mixture B leads to a reduction of these impurities in the reaction medium. Therefore, the amount of impurities is lower after hydrogenation than before hydrogenation.

The mole percentages of major by-products in the crude reaction mixture are reported as follows.

The overall performance of the conversion of reaction mixture B to KA oil was improved in the batch hydrogenation over Nickel Raney catalyst compared to that obtained with chromium catalyst. The conversion (or conversion) and KA oil yield of cyclohexylhydroperoxide is higher than that obtained with the chromium catalyst, and the formation of by-products is lower. Since the initial reaction mixture B already contained by-products prior to the hydrogenation reaction, the yield of by-products is negative. Cyclohexanol is the main product of CyOOH hydrogenation.

Example 3: General Procedure of Semi-Continuous Reaction Mixture B Hydrogenation over Nickel Raney Catalyst

In a dry atmosphere of N ₂ , 0.1 g of Nickel Raney catalyst was stirred with 5.6 g of cyclohexane in a hydrogenation autoclave. The temperature was raised to 60° C. and the total hydrogen pressure was 20 bar. 19 g of reaction mixture B was added dropwise at a mass flow of 15 g/h and hydrogenated. After 1.5 hours, the resulting crude reaction mixture was analyzed by gas chromatography. The results obtained are reported in the table below.

The mole percentages of major by-products in the crude reaction mixture are reported as follows.

The by-product yields are lower in the semi-continuous hydrogenation than those obtained batchwise.

Example 4: Effect of Temperature

In a dry atmosphere of N ₂ , 0.054 g of Nickel Raney catalyst was stirred in an autoclave with 5.6 g of cyclohexane. The temperature was raised to the set point value and the total hydrogen pressure was 20 bar. 12.32 g of reaction mixture B were added in one portion and hydrogenated. The resulting crude reaction mixture was analyzed by gas chromatography. The results obtained are reported in the table below.

The molar percentage of major by-products in the crude reaction mixture are reported as follows.

Catalytic activity was measured at each reaction temperature.

At lower temperatures more cyclohexanone was obtained, which means that the hydrogenation of cyclohexanone to cyclohexanol is a major side reaction.

Example 5: Reuse of catalyst

The procedure of Example 2 was followed. Thereafter, the recovered nickel Raney catalyst was added back to the system and hydrogenation was periodically performed at 60°C. The results obtained are reported in the table below.

Example 6: Hydrogenation of Reaction Mixture C

The procedure of Example 2 was followed except for the hydrogenation of reaction mixture C. In a dry atmosphere of N ₂ , 0.43 g of Nickel Raney catalyst was stirred together with 26 g of reaction mixture C containing approximately 10% of 6-hydroxyperoxycaproic acid (HPOCap). The temperature was raised to 60° C. and the total hydrogen pressure was 20 bar. After 1 hour, the conversion rate of HPOCap was 100%.

Example 7: Hydrogenation of Reaction Mixture A

The procedure of Example 4 was followed except for the hydrogenation of reaction mixture A. In a dry atmosphere of N ₂ , 0.061 g of Nickel Raney catalyst was stirred with 5.7 g of cyclohexane. The temperature was raised to 60° C. and the total hydrogen pressure was 20 bar. 12.7 g of reaction mixture A containing approximately 6.5% hydroperoxide (CyOOH + HPOCap) was added to the autoclave in one portion and hydrogenated. The resulting crude reaction mixture was analyzed by gas chromatography. The results obtained are reported in the table below.

*TT _HPOCap = conversion rate of HPOCap

Claims (12)

A process for preparing a mixture containing cyclohexanol and cyclohexanone comprising hydrogenating cyclohexyl hydroperoxide in cyclohexane in the presence of a Raney nickel catalyst to provide cyclohexanol and cyclohexanone As,
a) oxidizing cyclohexane with molecular oxygen to provide a reaction mixture comprising cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, 6-hydroxyperoxycaproic acid and unconverted cyclohexane;
b) hydrogenating cyclohexyl hydroperoxide in the presence of a Raney nickel catalyst to provide cyclohexanol and cyclohexanone;
Prior to step b), the reaction mixture obtained in step a) was extracted with water to obtain an organic phase containing cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone and unconverted cyclohexane and 6-hydroxyperoxycaproic acid A process for preparing an aqueous phase containing The process of claim 1 wherein 6-hydroxyperoxycaproic acid is hydrogenated in the presence of a Raney nickel catalyst to provide 6-hydroxycaproic acid. The process according to claim 1 , wherein 6-hydroxyperoxycaproic acid is hydrogenated in an aqueous phase in the presence of a Raney nickel catalyst to provide 6-hydroxycaproic acid. A method for producing adipic acid, comprising:
a) oxidizing cyclohexane with molecular oxygen to provide a reaction mixture comprising cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, 6-hydroxyperoxycaproic acid and unconverted cyclohexane;
b) hydrogenating cyclohexyl hydroperoxide in the presence of a Raney nickel catalyst to provide cyclohexanol and cyclohexanone;
c) oxidation of cyclohexanol and cyclohexanone with nitric acid to provide adipic acid;
Prior to step b), the reaction mixture obtained in step a) was extracted with water to obtain an organic phase containing cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone and unconverted cyclohexane and 6-hydroxyperoxycaproic acid A process for preparing an aqueous phase containing 5. The process of claim 4 wherein 6-hydroxyperoxycaproic acid is hydrogenated in the presence of a Raney nickel catalyst to provide 6-hydroxycaproic acid. 5. The process according to claim 4, wherein 6-hydroxyperoxycaproic acid is hydrogenated in an aqueous phase in the presence of a Raney nickel catalyst to provide 6-hydroxycaproic acid. A process for the preparation of 6-hydroxycaproic acid, comprising the step of hydrogenating 6-hydroxyperoxycaproic acid in the presence of a Raney nickel catalyst. 8. The method of claim 7,
a) oxidizing cyclohexane with molecular oxygen to provide a reaction mixture comprising cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, 6-hydroxyperoxycaproic acid and unconverted cyclohexane;
b1) hydrogenating 6-hydroxyperoxycaproic acid in the presence of a Raney nickel catalyst to provide 6-hydroxycaproic acid. The process according to claim 8, wherein step b1) is carried out in the reaction mixture obtained in step a). 9. The organic phase according to claim 8, wherein prior to step b1), the reaction mixture obtained in step a) is extracted with water and the organic phase containing cyclohexyl hydroperoxide, cyclohexane, cyclohexanone and unconverted cyclohexane and 6-hydro An aqueous phase containing hydroxyperoxycaproic acid is provided, and step b) is performed in the aqueous phase. A method for preparing epsilon-caprolactam, comprising:
a) oxidizing cyclohexane with molecular oxygen to provide a reaction mixture comprising cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, 6-hydroxyperoxycaproic acid and unconverted cyclohexane;
b) hydrogenating cyclohexyl hydroperoxide in the presence of a Raney nickel catalyst to provide cyclohexanol and cyclohexanone;
c) purifying cyclohexanol and cyclohexane optionally by distillation;
d) optionally separating cyclohexanone from cyclohexanol;
e) dehydrogenating cyclohexanol to cyclohexanone;
f) converting cyclohexanone to epsilon-caprolactam,
Prior to step b), the reaction mixture obtained in step a) was extracted with water to obtain an organic phase containing cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone and unconverted cyclohexane and 6-hydroxyperoxycaproic acid A process for preparing an aqueous phase containing 12. The method of claim 11
a) oxidizing cyclohexane with molecular oxygen to provide a reaction mixture comprising cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, 6-hydroxyperoxycaproic acid and unconverted cyclohexane;
b) hydrogenating cyclohexyl hydroperoxide in the presence of a Raney nickel catalyst to provide cyclohexanol and cyclohexanone;
c) purifying cyclohexanol and cyclohexanone optionally by distillation;
d) optionally separating cyclohexanone from cyclohexanol;
e) dehydrogenating cyclohexanol to cyclohexanone<
f1) reacting cyclohexanone with hydroxylamine or a salt thereof to give cyclohexanone oxime;
f2) reacting cyclohexanone oxime to provide epsilon-caprolactam,
Prior to step b), the reaction mixture obtained in step a) was extracted with water to obtain an organic phase containing cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone and unconverted cyclohexane and 6-hydroxyperoxycaproic acid A process for preparing an aqueous phase containing